1. Field of the Invention
The present invention relates to a laser processing apparatus which performs a processing by irradiating a laser beam emitted from a laser oscillator onto a surface of a workpiece through a condenser lens which condenses the laser beam on the workpiece.
2. Description of the Related Arts
When using laser beams in the processing of a workpiece, it is a routine practice to change the laser beams to the desired size and shape according to the workpiece. A typical example of a specific method for changing the shape of laser beams involves changing the beam shape by moving 2 or more lenses.
In this method, a mechanism is required for moving the lenses, but there is a limit to the speed at which such a lens-moving mechanism is capable of responding in cases where processing of a workpiece is to be performed at high speeds or in cases where adjustment change to the desired beam shape is to be made rapidly, thus resulting in the drawback that it cannot be used.
Accordingly, in order to eliminate this drawback, a laser processing apparatus was disclosed which adjusts to the desired beam shape at high speeds by deforming microdeformation mirrors by means of actuators (e.g., Japanese Patent Application Kokai Publication No. 2006-7257).
In Patent Reference 1, there are no drawings illustrating the detailed structure of the microdeformation mirrors, but there is a description of a structure wherein electrodes serving as about 40 actuators are covered with a transparent film formed by coating, and the transparent film is caused to undergo microdeformation due to an electric drag force generated by the actuators.
However, in the case of such microdeformation mirrors, since the mirror surface at the time of deformation does not form a smooth curved surface, but tends, rather, to form a pseudo-curved surface, it is thought that discontinuities readily arise in laser beam intensity distribution.